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  • Author Author: embeddedguy
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Raspberry Pi RP2350 based PCB design

embeddedguy

Sometimes back, I was designing a PCB based on RP2350 and now I received the finished PCB. So this post is about the experience that I would like to share about my PCB design.

Firstly, the original plan of creating this PCB was to create RP2350 based Single Pair Ethernet development board. For that I had used ADIN-1111 chip. Unfortunately, it was not available during the PCBA making. Hence the original idea was not possible. But I have tested the RP2350 chip and it is working fine.  The design is based on KiCAD and is 4-layer design.

The easiest idea to test this board is to use Micropython so that the board can be tested fast. I tested a simple blink program on this board and it works fine.

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  • in reply to BigG

    And the board looks like it has paste already on the un-populated pads. To mount the chip it would need some flux, good enough placement and sufficient heat for assembly. 

  • in reply to embeddedguy

    You're right. They don't offer 10BASE-T1L chipset.

    I know TI do, and there's some nice reference material available online too. Wurth Eletronik, for example, also created a reference design based on TI chip.

    www.we-online.com/.../DP83TD510E-DP83TD510E-EVMl-LAN-POE

  • in reply to embeddedguy

    For future reference it is possible to hand solder (using a soldering iron) QFN parts like the ADIN chip.

    The trick is to make a footprint with a single large hole for the big centre pad. Make the hole as big as you can without breaking out of the pad.

    To solder the chip, apply solder past with a small pointy thing (I would use a needle in a holder)  - it doesn't matter if the paste bridges the outer pads but try not to bridge from the signal pads to the centre. Don't put any paste on the centre pad.

    Use a spring ar of some kind (I use a bit of bent "piano" wire held in a tiny vice) to hold the chip in place on the board and reflow the paste on the outer pads with a hot and very fine tipped soldering iron. It will need to be hot to get any heat down a really fine needle tip. Don't worry about bridging outer pads or soldering all of them.

    Once the paste has all been melted apply a lot of really runny flux (I use Warburtons 315))

    image

    You can get this from Rapid Electronics.

    Touch up the solder on the outer pads to solder any that are not and remove bridges. If there is too much solder remove some with solder wick. Keep it fluxy !

    Then solder the chip centre pad (if a connection is needed) using a bigger iron bit and some wire solder.

    Don't solder the centre pad unless you have to !

    The big centre hole concept is useful for removing chips even if you have a full reflow set up. Only do the multiple tiny holes thing if you need them for RF or thermal purposes.

    Obviously this isn't the ideal way to do things but if you need to add a QFN part after the rest of the board has been re-flowed it's the best cheap way I know. It can, of course, be done better if you have a fancy rework machine costing many £k and all the required add ons.

    It may help solder a QFN if you apply hot air to the underside of the board and get it up to about 120C.

    It is much, much easier to do all this with leaded solder - the unleaded stuff doesn't flow so well and has a much higher melting point.

    You can get ultra low melting point solder which might be even better but I have not tried it.

    MK

  • in reply to BigG

    Right. Thanks for this nice suggestion. 
    I will keep making PCBs and next time I will try to get when ordering the PCB.